# HydroCalc Plus vs C6协同v3.9

The clearest difference is price: C6协同v3.9 at Free against HydroCalc Plus's $3.99. C6协同v3.9 also leads on in-app purchases (none vs 4) and iOS requirement (7.0 vs 15.1). On update cadence, ads and device support there is nothing between them.

C6协同v3.9 is free to download; HydroCalc Plus costs $3.99 up front. HydroCalc Plus sells 4 one-off in-app purchases. C6协同v3.9 asks for nothing beyond the download.

Both ship on a similar rhythm, roughly every 3 weeks. The most recent releases landed on August 31, 2026 and September 17, 2026 respectively.

## The numbers

| Metric | HydroCalc Plus | C6协同v3.9 |
| --- | --- | --- |
| Price | $3.99 | **Free** |
| Rating | **[5.0 (1 ratings)](https://appshunter.io/ios/app/hydrocalc-plus/id578807688/reviews)** | — |
| Number of ratings | **1** | — |
| Positive reviews | 100.0% of reviews | — |
| In-app purchases | Yes | **No** |
| Ads | No | No |
| Update frequency | Every 3 weeks | Every 3 weeks |
| Monetization | Paid | — |
| Size | 34 MB | 21 MB |
| Requires iOS | 15.1 | **7.0** |
| Devices | **iPhone, iPad, iPod** | iPhone, iPod |
| Age rating | 4+ | 4+ |
| Developer | [Transparent Blue Water LLC](https://appshunter.io/developer/1847968351) | [BEIJING JINHER SOFTWARE CO.LTD.](https://appshunter.io/developer/473901494) |

## What reviewers say

### HydroCalc Plus

[App page](https://appshunter.io/ios/app/hydrocalc-plus/id578807688)

A professional tool for hydraulic engineers to calculate pressure losses in piping systems. It supports US and SI units, offers an extensive pipe material and fittings database, and includes inverse calculations for design optimization.

**Highlights:** Friction head loss calculation (Hazen-Williams), US and SI unit support, Extensive pipe material library, Fittings and valves database, Inverse calculation mode, Real-time results (velocity, losses)

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases (4)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Pump Power Calculator | $1.99 | one-time |
| System Curve Generator | $1.99 | one-time |
| Pipe Database | $1.99 | one-time |
| Industrial Fluids Pack | $2.99 | one-time |


### C6协同v3.9

[App page](https://appshunter.io/ios/app/c6v39/id1173412813)

**Features:** macOS Compatibility

**In-app purchases:** none


## Frequently asked questions

### Is HydroCalc Plus free?

HydroCalc Plus costs $3.99, and also offers in-app purchases.

### Is C6协同v3.9 free?

C6协同v3.9 is free to download, with no in-app purchases.

### Do HydroCalc Plus or C6协同v3.9 have ads?

Neither HydroCalc Plus nor C6协同v3.9 shows ads.

### Which is updated more often, HydroCalc Plus or C6协同v3.9?

HydroCalc Plus ships an update every 3 weeks, and C6协同v3.9 every 3 weeks. Most recently, HydroCalc Plus was updated on August 31, 2026 and C6协同v3.9 on September 17, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*